Smart Fortwo Diesel: Rough Shifting & Gearbox Troubles Fix

Had a similar issue with my 2011 Smart Fortwo CDI. As someone with some hands-on experience working on cars, those symptoms sounded very familiar. Started with rough shifting and gear grinding between changes. Initially thought it was just low gear oil, but the problem got worse over a few weeks. The workshop diagnosed defective gears in the transfer case causing mechanical wear. The transfer fluid was also contaminated with metal particles. The repair involved: Complete transfer case inspection, Replacement of worn gear components, Fresh transfer fluid, System pressure test Total cost was 330€ including parts and labor. The repair completely resolved the shifting issues and the transmission now works smoothly again. Before suggesting specific solutions, could you share: Current mileage, When was the last transfer fluid change, Any unusual noises during acceleration, Does the problem occur more when cold or warm, Service history regarding transmission work This info would help determine if your issue matches what I experienced and provide more targeted advice.

Current mileage is 154451 KM and yes, last full service was completed on schedule. The gear grinding noise is most noticeable during cold starts and gets slightly better after warm-up. The transfer fluid has not been changed since I got the car, which explains the increasing wear on transmission components. I hear a distinct clunking sound during acceleration, particularly between first and second gear. Checking the transfer case oil level revealed it was slightly below minimum, likely contributing to the gear wear issues. Will schedule a workshop visit to have the transfer fluid changed and transmission inspected properly.

Good that you checked the fluid level, running low on transfer fluid definitely matches the symptoms we both experienced. The clunking noise between first and second gear is a classic sign of gear wear in these Smart transmissions, just like what I dealt with. From my repair experience, letting the transfer fluid run too low usually leads to accelerated mechanical wear. Once metal particles start circulating in the degraded transfer fluid, the gear grinding tends to worsen quickly, especially during cold starts like you mentioned. My suggestion based on dealing with the same issue: Get the transfer fluid changed immediately before more gear wear occurs, Have them inspect for metal particles in the old fluid, Request a full pressure test of the transfer case, Consider a complete transfer case inspection if they find contamination The repair costs have likely increased since my fix, but catching it now while the gear grinding is still intermittent could prevent needing a full transfer case rebuild. The Smart transmission responds well to fresh transfer fluid when caught early enough. Let us know what the workshop finds. Since our cars are similar model years with comparable mileage, they might spot the same wear patterns I experienced.

Thanks for the detailed information. After reviewing your advice and comparing symptoms, I will definitely proceed with the workshop visit this week. The similarity between our transmission issues, especially the cold start gear grinding and low transfer fluid causing mechanical wear, is too close to ignore. The clunking noise during gear changes and your experience with metal particles in the transfer case fluid makes me think I caught this just in time. Getting the fluid changed and having them check for contamination seems like the smart move before the gear wear becomes more severe. Will update once I get the workshop report and cost estimate. Based on your repair experience of 330€, I can at least budget accordingly, though I expect prices may have increased. Hopefully, catching these symptoms early means I can avoid a complete transfer case rebuild like you mentioned.